1. Field of the Invention
The present invention relates to agricultural vehicles, and, more particularly, to guidance assisted agricultural vehicles.
2. Description of the Related Art
Agricultural vehicles and implements are commonly used to perform various agricultural functions, such as tilling, planting, spraying, and fertilizing. As modern farming methods have increased the yield of crops, many farming operations have seen increased costs associated with more advanced farming methods. Precise control of farming operations can increase the efficiency of the operations and reduce costs to the farmer. To this end, automation of farming operations can help increase the productivity and efficiency to lower the costs for farmers. One such example of farming operation automation is automatic guidance of various farm vehicles performing the farming operations.
Agricultural vehicles commonly utilize control systems connected to position sensing technology, such as global positioning systems (GPS), to provide automatic guidance control in performing these various agricultural functions. The automatic guidance control systems are capable of steering the vehicle with a high degree of accuracy. The automatic guidance control systems often operate by creating at least one original base guidance line, called an “AB line,” and then generating an array of adjacent guidance lines to be followed by the agricultural vehicle in performing its function. These adjacent guidance lines, or swaths, depend not only on the geometry of the original AB guidance line, but also upon the physical characteristics and limitations of the agricultural vehicle and/or any towed agricultural implements. Such physical characteristics and limitations may include width, location of the implement with respect to the vehicle, and limitations of movement, such as minimum turning radius.
Farmers often own multiple agricultural vehicles or implements built by different manufacturers. Further, some farmers may wish to have another party with a different agricultural vehicle perform various operations using the farmer's supplied guidance lines. The guidance lines that are created by the automatic guidance control systems of these different agricultural vehicles do so using different algorithms. As a result, the guidance lines often differ, especially as the adjacent guidance lines get further and further from the original AB guidance line. If the previous guidance lines were created by the automatic guidance control system algorithm of another manufacturer, the guidance lines created by the automatic guidance control system algorithm of an agricultural vehicle being utilized currently may not match. Without some way to account for this mismatch, the automatic guidance control system cannot accurately follow the desired guidance lines because the mismatch is a compounding error that will continue to increase as the vehicle travels further from the original guidance line.
One particular reason for the mismatch that occurs is due to the need for converting latitude and longitude coordinates that are obtained by, for example, a GPS system to a Cartesian coordinate system so that metrics such as distance can be calculated. Since latitude and longitude coordinates are measured in radians, corresponding to the curvature of the Earth, and Cartesian coordinates are assumed to lie on a flat two-dimensional plane, the latitude and longitude coordinates can be converted using the previously mentioned algorithm to account for the curvature of the Earth to produce the corresponding Cartesian x-y coordinates. To convert the latitude and longitude coordinates to Cartesian coordinates, different algorithms may rely on different assumptions such as the Earth being spherical or ellipsoidal, different values for the equatorial radius of eccentricity, compensation for altitude, etc. These differences can cause the generated guidance lines to considerably vary, depending on what assumptions are used to generate the guidance lines. Since the generated guidance lines are estimates based on the given latitude and longitude coordinates, there can also be rounding errors present in the generated guidance lines. One such rounding error can be in calculating the swath width, which can be the source of the mismatch that propagates through the system's calculations. Without some way to correct the miscalculated swath width, the mismatch can compound as previously described.
What is needed in the art is a way to compensate for different swath generating algorithms being used to more accurately and reliably control an automatically guided agricultural vehicle.